The invention relates generally to an automatic safety catch apparatus for supporting a suspended member in the event that the suspension system fails. The invention relates particularly to suspended members positioned above a person where the safety catch apparatus must positively engage and where the amount of drop of the supported member is extremely critical.
There are numerous devices in which a heavy member is supported by a suspension system and is periodically raised and lowered to positions along a vertical column. A common problem with such devices is that a failure of any portion of the suspension system may allow the suspended member to drop, thereby damaging the member and anything in the path of the dropping member. This problem is particularly critical in devices where the suspension system is positioned above a person. Such devices include suspended X-ray and nuclear imaging equipment. The equipment, weighing approximately four hundred pounds, is suspended directly above and closely to a recumbent patient undergoing analysis. A failure of the suspension system would obviously be critical to the safety of the patient. In addition, due to the close proximity of the suspensed weight above the patient, a system having an automatic safety catch which allows a free fall drop of more than one-quarter inch before locked engagement could also be critical to the safety of the patient. Another particular problem with such devices is that often there is only a partial loss of tension of the suspension system which permits a slow drop of the member, but which is insufficient to activate the safety catch. The slightest drop of the heavy suspended weight would be critical to the safety of the patient.
A common prior art safety catch for suspension systems uses a spring to sense a loss of tension and to activate a lug into the teeth of a drive sprocket. These devices typically require from one-half to two inches of free fall drop before locked engagement. If the inital tooth is not engaged, free fall drop continues until the next tooth rotates to the engaging lug. Another common prior art device uses electrical switches and solenoids to engage a brake as a safety catch for a suspension system. Such braking devices have considerable mass which requires time to position and permits a long free fall drop prior to locked engagement.
All such known prior art devices permit drops far exceeding one-quarter inch and are, therefore, not acceptable in critical suspended member systems. The prior art has resorted to expensive threaded lead screw drive systems to position and manipulate the suspended member. The prior art has also resorted to expensively over-designed and redundant suspension systems to assure safe operation of the suspended member.
Accordingly, one object of the present invention is to provide an automatic, positive safety catch apparatus for a suspended member in the event that the suspension system fails.
Another object of the invention is to provide a safety catch apparatus for a suspended member which allows a minimal drop of the member upon failure of the suspension system.
Another object of the invention is to provide a safety catch which will activate upon a partial release in tension of the system.
Another object of the invention is to provide a mechanical safety catch apparatus which is not expensive to produce and install and which does not require complex servicing.
Still a further object of the invention is to provide a safety catch apparatus which can be readily reset after engagement and subsequent repair of the failed suspension system.